A strong trend in consumer electronics is to consolidate disparate functions into a single device to minimize the frequency with which users need to carry multiple portable electronic devices. While different demographic segments desire different combinations of functions, an appreciable number of consumers have adopted mobile stations that have the capability to receive broadcast radio such as AM and FM in addition to their more traditional two-way communication functions, which were once predominantly voice communications but are increasingly voice and/or data. However, broadcast radio signals and two-way communications use fundamentally different transmission protocols, and mobile stations having a FM reception capability typically included separate antennas for the distinct communication types.
When an antenna is in resonance at a resonance frequency, there will be an electromagnetic (EM) wave excited corresponding to the resonance frequency. The operating length of the antenna is designed based on the wavelength λ of the intended resonance frequency, generally λ/n of a wavelength where n is an even integer. To avoid antenna breakage and enhance signal reception, the planar inverted-F antenna (PIFA) antenna has been recently developed that decreases operating length of an antenna structure to λ/4 in a PIFA, as compared to λ/2 typically used for whip antennas. For an example of a PIFA antenna, see co-assigned U.S. Pat. No. 6,646,610. Also, the PIFA can be placed above a ground plane and embedded within a durable housing of the mobile station, protecting the PIFA from damage and obscuring it from view. Most mobile stations operate in accordance with GSM 900 and/or GSM 1800, so their resonance frequency is 900 MHz or 1800 MHz. By contrast, in the United States the frequency band for broadcast FM radio is between 88 and 108 MHz. As wavelength is inversely proportional to frequency, reception of FM signals requires a longer antenna than reception of GSM signals.
To enable the same mobile station to receive broadcast FM radio signals as well as engage in traditional two-way (voice or data) communications, two antennas were generally used. The two-way communications antenna may have been a whip antenna or a PIFA, whereas the broadcast FM reception antenna was embodied in a wire leading to an earpiece or headset. Given the popularity of wireless headsets for listening to a mobile station's traditional two-way communications, it is envisioned that consumers would also support a wireless headset that will additionally receive broadcast FM signals, at least when they are not actively engaged in a telephone conversation or other two-way communication of data over traditional mobile phone links. Listening to broadcast radio through a mobile device's built-in speaker without the need for a headset as antenna is also desirable. As the wire of prior art headsets acted as the FM reception antenna, the anticipated consumer need is not readily evident. While there have been attempts at integrating an FM antenna internal to a mobile station, their reception quality has generally been poor.
One prior art innovation to effect the above result is disclosed in co-owned U.S. Pat. No. 6,466,173, herein incorporated by reference in its entirety, which describes a whip antenna transducer and a patch or PIFA antenna that is internal to the device, each connected to radio circuitry via a switch that is actuated based on the position of the whip antenna, extended or retracted. As such, only one antenna is coupled to receiving circuitry at any time. Another co-owned prior art invention, U.S. Pat. No. 6,486,835 B1, discloses detecting a position of a retractable antenna relative to a fixed antenna, and is incorporated by reference in its entirety as relevant to a switch actuated based on a position of a retractable antenna.
What is needed in the art is a mobile station or other portable electronic device that is enabled to receive both two-way communications and broadcast radio signals, at least broadcast FM radio signals, each with low loss characteristics and without the need for a conductor extending many times the length of the mobile station housing.